Acid treating of benzol



ACID TREATING OF BENZOL Filed OCT.. 26, 1957 ATTORNEY.

Patented Apr. 18, 1939 UNITED STATES PATENT GFFI-CE ACID TREAT'ING oFENzoL Ashton T. Scott, Ardmore, Pa., assignorrto The Sharples'Corporation, a corporation of Dela- Ware The present invention pertainsto the purification of materials of the general character of thebenz'cll and light oil fractions derived from coal tar and' similarproducts. These products :ivr willi hereinafter be referred to as lightoils. It hasV been customary to treat oils ofthis character withsulphuric acid, in order to remove from the oilconstituentswhich haveundesirable effects on A its stability,y odor and color. The object ofthe present invention has beento` improve upon the results obtained' bysuch acid treatment. More specifically it has been the object of theinvention to provide a process affording a higher yield of oil,. a morethorough separation of impurities from the oil and a more thoroughseparation of reaction products from the oil' than could be attained byprior art processes. The manner in which these results are attained inthe practice of the invention will be evidentfrom a reading 2 of thefollowing, description in the iight of the a1;-

tached flow sheet,.in which,

The single ligure is a diagrammatic representation of the process of theinvention.

Referring. to the drawing by reference characters, the entire process ispreferably performed during the continuous iiow of oil and reagents, asillustrated. In the illustrated embob'dnnent of the-invention,.the oilVto be purified is passed into confluence with sludge acidV fromcontainer Il),

3 this acidv being obtained from a subsequent acid treating step of theprocess as described hereinafter. The temperature during the reactionreaches` a point between 140` and 165F. In order that this temperaturemay bev maintained during4 the course of the reaction, the oil ispreferably heated toa temperature between 110 and 130 F. prior totreatment with the sludge acid. The mixture of oil and sludge acidpasses to the mixer II, where it is intensely mechanically agi- 40 tatedfor a brief period (usually between onehalt and two minutes) during. thecontinuous flow ofthe material. The agitator of the mixer I I dispersesthe acid in the oil in very" fine droplets, `.thereby causing thoroughcontact between the oil and-'sludge reagent and reaction ofthe sludgewith the impurities to be removed. By the' ernployment of relativelyhigh tericperaturesandv intense agitation, the sludge acid'is causedv tore'- Vact' rapidly with the undesired impurities, and

- thev temperature rises rapidly during." this re- 66 bythe fact thatthemateri'als undergo practically no further temperature increase afterleaving that mixer.

After leaving the mixing step II, the mixture isv passed through an agerI2, which is provided with 4a mechanical agitator operated at a lo`w 5speed to gently' churn the mixture of materials under treatment for aperiod varying between 2 and 1'0 minutes.

From the ager I2, the mixture is passed through ,Y a cooler I3, whichmay be any desired form of 1'0 continuous refrigerating apparatusdesigned to lowerv the temperature tofa point below F.

From the coolerv I3, the mixture' is passed to a continuous centrifugalseparator I4', where it is separated into sour oil and sludgerespectively. 1'5 The oil' from the centrifugal separator, like oil fromprior art processes of treatingv light oils, is contaminated with asmall ar'nountl of sludge, and it isY a primary object of the followingsteps of the process to remove that sludge. To this end, 20 the oil istreated with' concentrated sulphuric acid from container I5, andintimately mixed with that acid' in the mixer I6, the construction andoperation ofthe mixer IS'being similar to'that described above withrespect to mixer I'I. From 25 the mixer I6, the mixture passes to anager' II which is similarA` in' construction, and operated similarly to,ager I2.

While'the structure and details of operation of mixer I6 and ager II aresimilar to those of mixer I I and ager I2, the eiect of the operations.performed' in the mixer I'Ii'andi ager I I` is very `difierent fromthat inthe mixer I'I and ager' I2'. The operation performed in the mixerII causes a y vigorousV and rapid reaction between the sludge $5 acidland the impuritiesto be removed, while the function ofthe mixer I6 andager I'I4 is to cause solution or physicalv combination of sludgeremaining'inthe oil discharged from centrifuge I4' with acid fromcontainer I5 and thus tol enable 40 the residual sludge to be'separated' in the centrifuge I8, together with the acid added at- I5.lIhisA difference in function is indicated by the tact that thetemperature of the oil increases by approximately 35 F. (e. g., from 120F. to 155 '45 F.) during passage through the mixer II, whereas there ispractically no increase intemperature as the oil passes through themixer I6. Y

In the practicel of the invention, attempt is made to obtain completereaction betweenv the im- 50 purities to be removed from the oil, andthe acid, in the mixer II and ager I2, and it is for this reason thatthe oil is heated prior to the mixing operation which is performed inthe mixer I I.

Havingl obtained substantially complete reac- *.55

tion of the sludge acid with the impurities, and removal of most of theresulting impurities together With the sludge acid by passage throughthe centrifuge I4, the function of the step of adding fresh concentratedacid is principally one of extracting the small traces of residualimpurities from the oil by solution in, or association with, thisconcentrated acid. In this step of treating the oil with freshconcentrated acid to remove residual impurities, reaction between theoil and this fresh acid is undesired, and the oil is therefore cooled ata stage of the process prior to the stage at which concentrated acid ispassed into coniiuence with the oil, this cooling step serving toprevent further chemical reaction between theoil and acid and to bringthe oil to a temperature at which the maximum effect of solution orassociation with the fresh acid is attained,

The mixture from the .ager I'I is passed through a continuous separatorI8, where it is separated into sludge acid and purified oil. The sludgeacid from the centrifuge I8 is passed to container I0 and used in thesubsequent practice of the process in the performance of the initialsteps of the process in the treatment of further oil. The oil from thecentrifuge I8 is treated with alkali from container I9 in order toneutralize this oil, the mixture of oil and alkali being intenselyagitated in the mixer 1Z0. The material from the mixer 20 passes to acontinuous centrifugal separator 2 I, where it is resolved into purifiedoil and an aqueous solution of the reaction product of the alkali withthe acid content of the oil.

Modifications will be obvious to those skilled in the art. Thus, thefundamental feature of the invention consists in the performance of thestep Vof initially mixing sludge acid with oil .at a relatively hightemperature to cause substantially complete reactionof the acid with theimpurities in this initial treating step, and in the lowering of thetemperature of the oil after separation of the resulting acid sludgefrom the oil 'in' order that the subsequent treatment with fresh acidmay be performed at a lower temperature best adapted to facilitateremoval of residual impurities from the oil without loss of oil byreaction which might occur if the subsequent treatment with concentratedacid were performed at higher temperatures.

It will be understood that, while a succession of two countercurrenttreating steps is disclosed, a larger number of countercurrent steps maybe employed in the practice of the process of the invention. It willalso be understood that the invention is not limited to the use of theparticular types of mixers andV agers described above, but that othertypes of apparatus designed to perform the functions of theseelementsmay be substituted in the practice of the process.

Stillffurther modifications will be obvious to those skilled inthe artand I do not therefore wish to be limited except by the scopeof thesub-joined claims.

I claim: ,Y

1. In the acid treatment of light oils, the steps comprising contactingthe oil toV be treated with acid sludge derived from the treatment oflight oil with concentra-ted sulphuric acid, thoroughly mixing thesludge acid and oil to cause reaction of the sludge acid with the oilwhile maintaining the oil at a temperature in excess of 130 F. andthereby effecting reaction of the sludge acid with substantially all ofthe impurities which have undesirable effects on its stability, odor andcolor, thereafter separating from the oil acid sludge resulting fromsaid reaction, and then mixing with fresh concentrated sulphuric acidthe oil so separated from the bulk of the sludge in order to dissolveresidual sludge in said fresh acid, and thereafter separating from thepuried oil,

sludge formed by said last-mentioned acid treat-V 2. In the acidtreatment of light oils, the steps comprising contacting the oil to betreated with acid sludge derived from the treatment of light oil withconcentrated sulphuric acid, thoroughly mixing the sludge .acid and oilto cause reaction of the sludge acid with the oil while maintaining theoil at a temperature in excess of 130 F. and thereby effecting reactionof the sludge acid with substantially all of the impurities which haveundesirable effects on its stability, odor and color, thereafterseparating from the oil acid sludge resulting from said reaction, andthen mixing at a temperature below F. with fresh concentrated sulphuricacid the oil so separated from the bulk of the sludge in order todissolve residual sludge in'said fresh acid, and thereafter separatingfrom the purified oil, sludge formed by said last-mentioned acidtheatment.

3. In the acid treatment of light oils, the steps comprising` contactingthe' oil to be treated with acid sludge derived from the treatment oflight oil With concentrated sulphuric acid, thoroughly mixing the sludgeacid and oil to cause reaction of theV sludge acid with the oil Whilemaintaining the oil at a temperature in excess of F. and therebyeffecting reaction of the sludge acid with substantially all of theimpurities which have undesirable effects on its stability, odor andcolor, thereafter separating from the oil acid sludge resulting fromsaid reaction, and then mixing with fresh concentrated sulphuric acid fthe oil so separated from the bulk of the sludge in order to dissolveresidualsludge in said fresh acid, thereafter separating from thepurified oil, sludge formed by said last-mentioned acid treatment, andusing sludge separated from the oil after said last-mentioned acidtreatment inthe treatment of further light oil.

ll. In the acid treatment, of light oils, the steps comprisingcontacting the oil to be treated with acid sludge derived from thetreatment of light oil with concentrated sulphuric acid, thoroughlymixing the sludge acid and oil to cause reaction of the sludge acid withthe oil while maintaining the oil at a temperature in excess of 130 F.and thereby effecting reaction of the sludge'acid with substantially allof the impurities ywhich have undesirable effects on its stability, odorand color, thereafter separating from the oil acid sludge resulting fromsaid reaction, and then mixing at a temperature below 120 1i'. withfresh concentrated sulphuric acid the oil so separated from the bulk ofthe sludge in order to dissolve residual sludge in said fresh acid,thereafter separating from the purified foil, sludge formed by saidlast-mentioned ,acid treatment, Vand using sludge separated from the oilafter'said lastf mentionedracid rtreatment in the treatment; of furtherlight oi1, l

Y 5. In the acid treatment of light oils, the steps comprisingcontacting the oil to be treated withL acid sludge derived from thetreatmentoflight of the sludge acid with the oil while maintaining theoil at a temperature in excessrof 130 F. and

rthereby effecting reaction of the sludge acid with substantially al1 ofthe impurities which have undesirable effects on its stability, odor andcolor, thereafter separating from the oil acid sludge resulting fromsaid reaction, and then mixing with fresh concentrated sulphuric acidthe oil so separated from the bulk of the sludge in order to dissolveresidual sludge in said fresh acid, and thereafter centrifug'ing fromthe puri- 10 ed oil, sludge formed by said last-mentioned acidtreatment.

6. In the acid treatment of light oils, the steps comprising contactingthe oil to be treated with acid sludge derived from the treatment oflight 1Il oil with concentrated sulphuric acid, thoroughly mixing thesludge acid and oil to cause reaction of the sludge acid with the oilWhile maintaining the oil at a temperature in excess of 130 F. andthereby effecting reaction of the sludge acid with substantially al1 -ofthe impurities which have undesirable effects on its stability, odor andcolor, thereafter centrifuging from the oil acid sludge resulting fromsaid reaction, and then mixing with fresh concentrated sulphuric acidthe oil so separated from the bulk of the sludge in order to dissolveresidual sludge in said fresh acid, .and thereafter centrifuging fromthe purified oil, sludge formed by said last-mentioned acid treatment.

ASHTON T. SCO'I'I.

